The purpose of this application is to request funds to establish a multi-user facility for fluorescence studies of cellular chemistry and structure. The instrumentation requested for this facility is as follows: 1) a combination spectrofluorometer and microscope excitation system; 2) an inverted microscope; 3) an image intensifying video camera and image processor; 4) a high-resolution video recorder; 5) a micromanipulator and vibration-free table. These items will comprise a single, working unit dedicated to the following projects, all of which require the sensitivity and specificity of fluorescence: 1) The role of Ca++ and H+ ions in ligand activated cellular responses; 2) Pinocytotic regulation in normal and transformed cells and its relation to cell size and microtubular structure; 3) H+ gradients along endocytic pathways in a polarized cell: pH in "endosomal tubules" and "giant lysosomes" of absorptive cells in neonatal rat ileum; 4) Mechanism of cell-matrix interaction during cell migration; and 5) Interaction of matrix molecules with embryonic epithelia. The requested instrumentation has been selected for an overall flexibility and versatility which meets the requirements of the five diverse projects described herein, and which anticipates future facility requirements arising from newly developed fluorescence techniques.